The present invention relates to a process for the preparation of a lithium vanadium oxide, to the compound obtained and to its use as active material of a positive electrode.
Batteries comprising a positive electrode and a negative electrode separated by an electrolyte comprising a lithium salt in solution in a solvent are widely known. The operation of these batteries is provided by the reversible circulation of lithium ions in the electrolyte between the electrodes. The positive electrode is generally composed of a composite material comprising an active material, a binder, a material conferring electron conduction and optionally a compound conferring ionic conduction. The compound conferring electron conduction can be a carbon black which does not catalyze the oxidation of the electrolyte at a high potential.
The use is known of lithium vanadium oxides Li1+αV3O8 (0.1≦α≦0.25) as positive electrode active material. Various processes for the preparation of these compounds are known. A particularly advantageous process consists in preparing a precursor gel of the mixed oxide, in drying the gel and in then subjecting it to a heat treatment. Thus, S. Jouanneau et al. [J. Mater. Chem., 2003, 13, 921-927] describe a process which consists in preparing a gel by adding V2O5 to an aqueous LiOH.H2O solution, in drying the gel obtained after maturing at 50° C. with stirring for 24 hours and in then subjecting the xerogel obtained to a heat treatment at 350° C. or at 650° C. for 10 hours. The disadvantage of this process is that it employs a heat treatment over a long period of time, the energy thus required significantly increasing the production cost.
The present inventors have now found that an oxide Li1+αV3O8 having properties at least equivalent to those of the oxide of the above prior art can be obtained by a similar process in which the heat treatment is carried out for a time ranging from a few minutes to 1 hour.
The aim of the present invention is to provide a simple and inexpensive process for the preparation of an oxide Li1+αV3O8 (0≦α≦0.25).